I've found that "generic" exhaust systems, "H" pipe, muffler and pipes, over the axle pipes, have had fit problems, all of which were fixable. The resonators from the kits were made wrong, not "squeezed" at the sides.
The biggest problem was with the hangers:
- the mounting plates from inside the car (ref 64-65 Chassis Manual, Ford 5B236), used the wrong size stud, and were without the lead point.
- the insulator hanger at the rear (Ford 5266), wrong bends, not stamped properly.
- the insulator at the rear (Ford 5A261), too thin.
- the two mount to the frame rail (Ford 5A571 LH, 5A235 RH), formed wrong, metal too thin.
- the four carriage bolts, 23530-S2, are supplied as a full length thread, they should be threaded about an inch.
Ironically the two insulators from the body at the seats to the rear of the mufflers (Ford 5A242) was very accurate.
Most of those "problems" have been corrected. But some of the above a friend got earlier this year were still incorrect.
Jim